When must a flag be lowered to half-staff? Though precedent is often followed, there are also guidelines outlined by President Dwight D. Eisenhower in a 1954 proclamation. Aside from the instances outlined by Eisenhower, the president can also choose to lower a flag whenever the nation is mourning, whether it is after a tragedy or after the death of another official not outlined in the proclamation.

Vice president, the chief justice or a retired chief justice of the United States Supreme Court, or the speaker of the House of Representatives: 10 days

Associate justice of the Supreme Court, a member of the Cabinet, a former vice president, the president pro tempore of the Senate, the majority leader of the Senate, the minority leader of the Senate, the majority leader of the House of Representatives, or the minority leader of the House of Representatives: Death until interment

United States senator, representative, territorial delegate, or the resident commissioner from the Commonwealth of Puerto Rico: On the day of death and the day after

The governor of a state, territory or possession: Day of death until interment